Light weight and durable intake manifolds for internal combustion engines can be constructed of moldable thermoplastic synthetic resin material. Such intake manifolds may be constructed of a plurality of molded sections or shells which are joined together, for example, by vibration welding, friction welding or sonic welding. Typically, such intake manifolds are made up of three sections: an upper shell, a middle shell and a lower shell. A plenum chamber is formed between the middle and lower shells, and a plurality of intake channels which lead to the individual cylinders of the engine are formed between the upper and middle shells.
Intake manifolds require inlet openings for attached sensors such as a manifold absolute pressure sensor (MAP sensor) and/or introduction of secondary gases such as purge gases from an evaporative emission control system into the manifold. The MAP sensor provides manifold pressure information to a fuel injected engine's electronic control unit which is used to compute air density and determine the engine's air mass flow rate in order to calculate the appropriate fuel flow. The purge gas inlet is connected to the fuel vapor storage canister of the evaporative emission control system and allows a vacuum within the manifold to draw stored fuel vapors from the canister into the manifold to be mixed with the normal fuel/air mixture burned in the engine. In conventional intake manifolds, the MAP sensor and purge gas connections comprise individual passages in the upper shell of the manifold which open into the throttle body passage. The MAP and purge gas passages are each formed by a long, round pin in the upper shell molding tool to create the respective passage. To enable opening of the mold and ejection of the molded section, the pin typically is mounted on a retractable slide in the molding tool. Production of such molding tools involves high tooling costs. Also, the pin is a very high maintenance due to wear of the tool, and if the passage is long, it makes the pin easier to break.